Date: Erev Rosh Chodesh Av 5561
From: Rabbi Moshe Sofer
To: Rabbi Meir Pal
The Chasam Sofer upholds the Rema's ruling that a nursing woman who sees blood during marital relations three times becomes forbidden to her husband. He demonstrates that since the Ramban holds a nursing woman can establish a full veses, and even the Ra'avad and Rashba agree there is at least a chashash during nursing, three sightings properly trigger the prohibition of ro'eh machamas tashmish. He also resolves the Shach's distinction between yemei tohar and ordinary nursing days, and proposes a textual emendation to the Rashba's Toras HaBayis.
Source: Shu"t Chasam Sofer YD §143